1. Field of the Invention
The present invention relates to an image forming apparatus including a sheet feeding cassette detachably mounted in a main body of the image forming apparatus and the sheet feeding cassette.
2. Description of the Related Art
Conventionally, an image forming apparatus including a center-registration type sheet feeding cassette adapted for storing a recording sheet to be supplied to a main body of the apparatus and detachably mounted in the main body (for example, refer to the Japanese Unexamined Patent Publication No. 2003-212359) is known.
Such conventional sheet feeding cassette as disclosed in the above-described patent document includes a pair of cursors for regulating a width size of a recording sheet stored in the sheet feeding cassette and is so constructed as to determine a position of the recording sheet in a width direction by moving the pair of cursors in conjunction with each other by the way of a rack provided on each of the pair of cursors and a pinion provided between the racks so as to be engaged with each of the racks. Further, the pinion is rotatably supported by a boss fixed on a bottom surface portion of the sheet feeding cassette.
However, in the sheet feeding cassette having the above-described construction, in the case where a disproportionate external force is applied to each cursor when a stack of recording sheets comes in contact with one of the cursors strongly at the time when the recording sheets are supplied to the sheet feeding cassette, the two disproportionate external forces transmitted to the pinion through the rack connected to each cursor urge the pinion to move in a radial direction. Accordingly, a load is applied to the pinion and the boss supporting the pinion and causes a problem that the boss and the pinion are damaged.
Especially, in an image forming apparatus which is so constructed that a sheet feeding direction of a recording sheet from the sheet feeding cassette to the main body is substantially perpendicular to an insertion and withdrawal direction of the sheet feeding cassette with respect to the main body, a pair of cursors face each other in the insertion and withdrawal direction and a cursor located at a near side in the insertion direction is generally fixed by a stopper member and the like at a predetermined position based on a size of a recording sheet to be stored in the sheet feeding cassette. Accordingly, at the time when the sheet feeding cassette is mounted in the image forming apparatus, a great impact force (external force) generated by an inertial force of the recording sheet to be stored in the sheet feeding cassette is applied to the cursor positioned at a back side in the insertion direction. Accordingly, since an excessively great load is applied to the pinion and the boss supporting the pinion, the above-described problem that the boss and the pinion is broken becomes more apparent.